Surfactant peptide nanostructures and uses in drug delivery

ABSTRACT

Disclosed herein are surfactant peptide nanostructures wherein the peptides have repeating hydrophobic amino acids in an integer equal to or less than four. The peptide nanostructures are useful for therapeutic applications, including for delivery of drugs and siRNA.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application No. 62/599,566, filed Dec. 15, 2017, the contents of which are hereby incorporated by reference herein in their entirety.

SEQUENCE LISTING

The instant application contains a Sequence Listing which has been filed electronically in ASCII format and is hereby incorporated by reference in its entirety. Said ASCII copy, created on Nov. 30, 2018, is named 2004837-0227_SL.txt and is 29,249 bytes in size.

BACKGROUND

Surfactant peptides typically have a hydrophilic head group and a lipophilic tail having hydrophobic amino acids. Certain surfactant peptides have previously been disclosed (e.g., PCT Publication Numbers WO2003006043, WO2013181511, and WO2009018467). Some of the disclosed surfactant peptides are oligopeptides and di- and tri-block peptide copolymers with structures including a hydrophilic head group containing charged amino acids and a lipophilic tail containing hydrophobic amino acids in repeating units of 5 or more amino acids.

Other surfactant peptides, having a single repeating unit of four alanines, have been disclosed for use in stabilizing membrane proteins (e.g., US Patent Publication Number US20090069547).

SUMMARY

Previously disclosed surfactant peptides have been reported to self-assemble to form nanotubes having an average diameter of about 50 nM.

The present disclosure provides short surfactant peptides having a repeating hydrophobic unit of 4 or fewer amino acids that form nanospheric structures. Such nanospheric structures are particularly useful for formulation and delivery of therapeutic agents.

In some embodiments, the present disclosure provides compositions comprising peptides having repeating hydrophobic amino acids according to a formula of:

(N→C): (X)a(Y)m  Formula I

(N→C): (Y)m(X)a  Formula II

(N→C): (X)a(Y)m(X)b  Formula III

(N→C): (Y)m(X)a(Y)n  Formula IV

(N→C): (X)a(Z)m  Formula V

(N→C): (Z)m(X)a  Formula VI

(N→C): (X)a(Z)m(X)b; or  Formula VII

(N→C): (Z)m(X)a(Z)n;  Formula VIII

-   -   wherein (X) is an amino acid having a nonpolar and noncharged         sidechain at physiological pH;     -   (Y) is an amino acid having a cationic sidechain at         physiological pH;     -   (Z) is an amino acid having an anionic sidechain at         physiological pH; and wherein     -   a is an integer equal to or less than 4;     -   b is an integer equal to or less than 4;     -   m is an integer equal to or greater than 1; and     -   n is an integer equal to or greater than 1.

In some embodiments the peptide has a nanospheric structure. In some embodiments, the peptide forms a nanosphere. In some embodiments, the peptide forms a nanospheric structure with a center that is substantially free of self-assembling surfactant peptide. (e.g., a spherical nanovesicle).

In some embodiments, the amino acid of (X), (Y), and/or (Z) is a natural amino acid. In some embodiments, the amino acid of (X), (Y), and/or (Z) is a non-natural amino acid.

In some embodiments, the integer of a or b is 4. In some embodiments, the integer of a or b is 3.

In some embodiments, (X) is alanine, valine, leucine, isoleucine, methionine, phenylalanine, tryptophan, or glycine. In some embodiments, (X) is alanine. In some embodiments, (Y) is arginine, lysine, histidine, or ornithine. In some embodiments, (Y) is lysine. In some embodiments, (X) is alanine and (Y) is lysine. In some embodiments, (Z) is aspartatic acid or glutamic acid.

In some embodiments, one or more amino acids is an L-amino acid. In some embodiments, each amino acid is an L-amino acid. In some embodiments, one or more amino acids is a D-amino acid. In some embodiments, each amino acid is a D-amino acid.

In some embodiments, the peptide is 4-10 amino acids in length. In some embodiments, the peptide is 5 amino acids in length. In some embodiments, the peptide is 6 amino acids in length. In some embodiments, the peptide is 7 amino acids in length.

In some embodiments, the peptide comprises a modified N- and/or C-terminus. In some embodiments the peptide has an acetylated N-terminus and/or an aminated C-terminus.

In some embodiments, peptides have a nanospheric structure and an amino acid sequence according to any of SEQ ID NOs: 1-50. In some embodiments, peptides have a nanospheric structure and an amino acid sequence according to any one of SEQ ID NOs: 51-100.

In some embodiments, peptides have a nanospheric structure and an amino acid sequence of AAAK (SEQ ID NO:1). In some embodiments, peptides have a nanospheric structure and an amino acid sequence of AAAAK (SEQ ID NO: 5). In some embodiments, peptides have a nanospheric structure and an amino acid sequence of AAAKAAA (SEQ ID NO: 15).

In some embodiments, the disclosure provides compositions comprising nanospheric peptides in an aqueous solution. In some embodiments, the peptide is at a concentration of at least 0.01% (w/v). In some embodiments, the aqueous solution has a pH of from about 6 to about 8. In some embodiments the aqueous solution has a pH of about 7. In some embodiments, the aqueous solution is at an ionic strength of from about 0 M to about 0.3 M. In some embodiments, the aqueous solution is at an ionic strength of about 0.15 M. In some embodiments, the aqueous solution is isotonic.

In some embodiments, the disclosure provides compositions for use in drug delivery. In some embodiments, the compositions comprise an agent for delivery to a subject. In some embodiments, the agent is a therapeutic. In some embodiments, the agent is a drug (e.g., a small molecule). In some embodiments, the agent is a biologic. In some embodiments, the agent is an oligonucleotide. In some embodiments, the agent is an inhibitor of RNA. In some embodiments, the agent is an siRNA. In some embodiments, the agent is for delivery to a cancer cell.

In some embodiments, the disclosure provides methods for formulating an agent for delivery to a subject, comprising a step of contact the agent with a nanospheric peptide surfactant as described herein.

In some embodiments, the disclosure provides methods of delivering an agent to a subject, the method comprising administering to the subject a composition formulated with a peptide having repeating hydrophobic amino acids according to a formula of:

(N→C): (X)a(Y)m  Formula I

(N→C): (Y)m(X)a  Formula II

(N→C): (X)a(Y)m(X)b  Formula III

(N→C): (Y)m(X)a(Y)n  Formula IV

(N→C): (X)a(Z)m  Formula V

(N→C): (Z)m(X)a  Formula VI

(N→C): (X)a(Z)m(X)b; or  Formula VII

(N→C): (Z)m(X)a(Z)n;  Formula VIII

-   -   wherein (X) is an amino acid having a nonpolar and noncharged         sidechain at physiological pH;     -   (Y) is an amino acid having a cationic sidechain at         physiological pH;     -   (Z) is an amino acid having an anionic sidechain at         physiological pH; and wherein     -   a is an integer equal to or less than 4;     -   b is an integer equal to or less than 4;     -   m is an integer equal to or greater than 1; and     -   n is an integer equal to or greater than 1.

In some embodiments, the peptide forms a nanospheric structure. In some embodiments, the peptide forms a nanosphere. In some embodiments, the peptide forms a spherical nanovesicle.

In some embodiments, the amino acid of (X), (Y), and/or (Z) is a natural amino acid. In some embodiments, the amino acid of (X), (Y), and/or (Z) is a non-natural amino acid.

In some embodiments, the integer of a or b is 4. In some embodiments, the integer of a or b is 3.

In some embodiments, (X) is alanine, valine, leucine, isoleucine, methionine, phenylalanine, tryptophan, or glycine. In some embodiments, (X) is alanine. In some embodiments, (Y) is arginine, lysine, histidine, or ornithine. In some embodiments, (Y) is lysine. In some embodiments, (X) is alanine and (Y) is lysine. In some embodiments, (Z) is aspartic acid or glutamic acid.

In some embodiments, one or more amino acids is an L-amino acid. In some embodiments, each amino acid is an L-amino acid. In some embodiments, one or more amino acids is a D-amino acid. In some embodiments, each amino acid is a D-amino acid.

In some embodiments, the peptide is 4-10 amino acids in length. In some embodiments, the peptide is 5 amino acids in length. In some embodiments, the peptide is 6 amino acids in length. In some embodiments, the peptide is 7 amino acids in length.

In some embodiments, the peptide comprises a modified N- and/or C-terminus. In some embodiments the peptide has an acetylated N-terminus and/or an aminated C-terminus.

In some embodiments, peptides have a nanospheric structure and an amino acid sequence according to any of SEQ ID NOs: 1-50. In some embodiments, peptides have a nanospheric structure and an amino acid sequence according to any one of SEQ ID NOs: 51-100.

In some embodiments, peptides have a nanospheric structure and an amino acid sequence of AAAK (SEQ ID NO:1). In some embodiments, peptides have a nanospheric structure and an amino acid sequence of AAAAK (SEQ ID NO: 5). In some embodiments, peptides have a nanospheric structure and an amino acid sequence of AAAKAAA (SEQ ID NO: 15).

In some embodiments, the disclosure provides compositions comprising nanospheric peptides in an aqueous solution. In some embodiments, the peptide is at a concentration of at least 0.01% (w/v). In some embodiments, the aqueous solution has a pH of from about 6 to about 8. In some embodiments the aqueous solution has a pH of about 7. In some embodiments, the aqueous solution is at an ionic strength of from about 0 M to about 0.3 M. In some embodiments, the aqueous solution is at an ionic strength of about 0.15 M. In some embodiments, the aqueous solution is isotonic.

Definitions

In order for the present disclosure to be more readily understood, certain terms are first defined below. Additional definitions for the following terms and other terms are set forth throughout the specification.

The term “agent” as used herein refers to a compound or entity of any chemical class including, for example, polypeptides, nucleic acids, saccharides, lipids, small molecules, metals, or combinations thereof. In some embodiments, an agent is or comprises a natural product in that it is found in and/or is obtained from nature. In some embodiments, an agent is or comprises one or more entities that are man-made in that it is designed, engineered, and/or produced through action of the hand of man and/or is not found in nature. In some embodiments, an agent may be utilized in isolated or pure form; in some embodiments, an agent may be utilized in crude form. Some particular agents that may be utilized in accordance with the present invention include small molecules, antibodies, antibody fragments, aptamers, nucleic acids (e.g., siRNAs, shRNAs, DNA/RNA hybrids, antisense oligonucleotides, and ribozymes), peptides, peptide mimetics, etc. In some embodiments, an agent is or comprises a polymer. In some embodiments, an agent is not a polymer and/or is substantially free of any polymer. In some embodiments, an agent contains at least one polymeric moiety. In some embodiments, an agent lacks or is substantially free of any polymeric moiety. In some embodiments, an agent is or comprises a cellular lysate.

As used herein, the term “amino acid,” in its broadest sense, refers to any compound and/or substance that can be incorporated into a polypeptide chain, e.g., through formation of one or more peptide bonds. In some embodiments, an amino acid has the general structure H₂N—C(H)(R)—COOH. In some embodiments, an amino acid is a naturally-occurring amino acid. In some embodiments, an amino acid is a synthetic amino acid; in some embodiments, an amino acid is a D-amino acid; in some embodiments, an amino acid is an L-amino acid. “Standard amino acid” refers to any of the twenty standard L-amino acids commonly found in naturally occurring peptides. “Nonstandard amino acid” refers to any amino acid, other than the standard amino acids, regardless of whether it is prepared synthetically or obtained from a natural source. In some embodiments, an amino acid, including a carboxy- and/or amino-terminal amino acid in a polypeptide, can contain a structural modification as compared with the general structure above. For example, in some embodiments, an amino acid may be modified by methylation, amidation, acetylation, and/or substitution as compared with the general structure. As will be clear from context, in some embodiments, the term “amino acid” is used to refer to a free amino acid; in some embodiments it is used to refer to an amino acid residue of a polypeptide.

As used herein, the term “approximately” or “about,” as applied to one or more values of interest, refers to a value that is similar to a stated reference value. In certain embodiments, the term “approximately” or “about” refers to a range of values that fall within 25%, 20%, 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, or less in either direction (greater than or less than) of the stated reference value unless otherwise stated or otherwise evident from the context (except where such number would exceed 100% of a possible value).

Two events or entities are “associated” with one another, as that term is used herein, if the presence, level and/or form of one is correlated with that of the other. In some embodiments, two or more entities are physically “associated” with one another if they interact, directly or indirectly, so that they are and/or remain in physical proximity with one another. In some embodiments, two or more entities that are physically associated with one another are covalently linked to one another; in some embodiments, two or more entities that are physically associated with one another are not covalently linked to one another but are non-covalently associated, for example by means of hydrogen bonds, van der Waals interaction, hydrophobic interactions, magnetism, and combinations thereof.

The term “comparable” is used herein to describe two (or more) sets of conditions, circumstances, individuals, or populations that are sufficiently similar to one another to permit comparison of results obtained or phenomena observed. In some embodiments, comparable sets of conditions, circumstances, individuals, or populations are characterized by a plurality of substantially identical features and one or a small number of varied features. Those of ordinary skill in the art will appreciate that sets of circumstances, individuals, or populations are comparable to one another when characterized by a sufficient number and type of substantially identical features to warrant a reasonable conclusion that differences in results obtained or phenomena observed under or with different sets of circumstances, individuals, or populations are caused by or indicative of the variation in those features that are varied. Those skilled in the art will appreciate that relative language used herein (e.g., enhanced, activated, reduced, inhibited, etc.) will typically refer to comparisons made under comparable conditions.

By “complementary” is meant capable of forming ionic or hydrogen bonding interactions between hydrophilic residues from adjacent peptides, e.g., in a sheet or scaffold, each hydrophilic residue in a peptide either hydrogen bonds or ionically pairs with a hydrophilic residue on an adjacent peptide or is exposed to solvent.

Certain methodologies may include a step of “determining”. Those of ordinary skill in the art, reading the present specification, will appreciate that such “determining” can utilize or be accomplished through use of any of a variety of techniques available to those skilled in the art, including for example specific techniques explicitly referred to herein. In some embodiments, determining involves manipulation of a physical sample. In some embodiments, determining involves consideration and/or manipulation of data or information, for example utilizing a computer or other processing unit adapted to perform a relevant analysis. In some embodiments, determining involves receiving relevant information and/or materials from a source. In some embodiments, determining involves comparing one or more features of a sample or entity to a comparable reference.

The term “in vitro” as used herein refers to events that occur in an artificial environment, e.g., in a test tube or reaction vessel, in cell culture, etc., rather than within a multi-cellular organism.

The term “in vivo” as used herein refers to events that occur within a multi-cellular organism, such as a human and a non-human animal. In the context of cell-based systems, the term may be used to refer to events that occur within a living cell (as opposed to, for example, in vitro systems).

As used herein, the term “nanospheric” refers to spherical structures having a diameter in the nanometer range. As used herein, a “nanospheric structure” includes nanospheres and/or spherical nanovesicles. A spherical nanovesicle is similar to a nanosphere but has a center that is substantially free of self-assembling surfactant peptide.

The term “peptide” as used herein refers to any polymeric chain of amino acids. In some embodiments, a peptide has an amino acid sequence that occurs in nature. In some embodiments, a peptide has an amino acid sequence that does not occur in nature. In some embodiments, a peptide has an amino acid sequence that is engineered in that it is designed and/or produced through action of the hand of man. In some embodiments, a peptide comprises or consists of natural amino acids, non-natural amino acids, or both. In some embodiments, a peptide comprises or consists of only natural amino acids or only non-natural amino acids. In some embodiments, a peptide comprises D-amino acids, L-amino acids, or both. In some embodiments, a peptide comprises only D-amino acids. In some embodiments, a peptide comprises only L-amino acids. In some embodiments, a peptide includes one or more pendant groups or other modifications, e.g., modifying or attached to one or more amino acid side chains, at the peptide's N-terminus, at the peptide's C-terminus, or any combination thereof. In some embodiments, such pendant groups or modifications are selected from acetylation, amidation, lipidation, methylation, pegylation, etc., including combinations thereof. In some embodiments, the term “peptide” may be appended to a name of a reference peptide, activity, or structure; in such instances it is used herein to refer to peptides that share the relevant activity or structure and thus can be considered to be members of the same class or family of peptides. For each such class, the present specification provides and/or those skilled in the art will be aware of exemplary peptides within the class whose amino acid sequences and/or functions are known; in some embodiments, such exemplary peptides are reference peptides for the peptide class or family. In some embodiments, a member of a peptide class or family shows significant sequence homology or identity with, shares a common sequence motif (e.g., a characteristic sequence element) with, and/or shares a common activity (in some embodiments at a comparable level or within a designated range) with a reference peptide of the class; in some embodiments with all peptides within the class.

The term “pure” is used to indicate the extent to which the peptides described herein are free of other chemical species, including deletion adducts of the peptide and peptides of differing lengths.

The term “reference” as used herein describes a standard or control relative to which a comparison is performed. For example, in some embodiments, an agent, animal, individual, population, sample, sequence or value of interest is compared with a reference or control agent, animal, individual, population, sample, sequence or value. In some embodiments, a reference or control is tested and/or determined substantially simultaneously with the testing or determination of interest. In some embodiments, a reference or control is a historical reference or control, optionally embodied in a tangible medium. Typically, as would be understood by those skilled in the art, a reference or control is determined or characterized under comparable conditions or circumstances to those under assessment. Those skilled in the art will appreciate when sufficient similarities are present to justify reliance on and/or comparison to a particular possible reference or control.

The term “self-assembling” is used herein in reference to certain peptides that, under appropriate conditions, can spontaneously self-associate into structures in solution (e.g., aqueous solutions), such as, nanospheric structures including nanospheres and spherical nanovesicles. In some embodiments, self-assembly (and/or dis-assembly) into nanospheric structures is responsive to one or more environmental triggers (e.g., change in one or more of pH, temperature, ionic strength, osmolarity, osmolality, applied pressure, applied shear stress, etc.). In some embodiments, compositions of self-assembling polypeptides are characterized by detectable nanospheric structure when the polypeptides are in an assembled state.

As used herein, the term “substantially” refers to the qualitative condition of exhibiting total or near-total extent or degree of a characteristic or property of interest. One of ordinary skill in the biological arts will understand that biological and chemical phenomena rarely, if ever, go to completion and/or proceed to completeness or achieve or avoid an absolute result. The term “substantially” is therefore used herein to capture the potential lack of completeness inherent in many biological and chemical phenomena.

As used herein, the phrase “therapeutic agent” in general refers to any agent that elicits a desired pharmacological effect when administered to an organism. In some embodiments, an agent is considered to be a therapeutic agent if it demonstrates a statistically significant effect across an appropriate population. In some embodiments, the appropriate population may be a population of model organisms. In some embodiments, an appropriate population may be defined by various criteria, such as a certain age group, gender, genetic background, preexisting clinical conditions, etc. In some embodiments, a therapeutic agent is a substance that can be used to alleviate, ameliorate, relieve, inhibit, prevent, delay onset of, reduce severity of, and/or reduce incidence of one or more symptoms or features of a disease, disorder, and/or condition. In some embodiments, a “therapeutic agent” is an agent that has been or is required to be approved by a government agency before it can be marketed for administration to humans. In some embodiments, a “therapeutic agent” is an agent for which a medical prescription is required for administration to humans.

As used herein, a “therapeutically effective amount” is an amount that produces the desired effect for which it is administered. In some embodiments, the term refers to an amount that is sufficient, when administered to a population suffering from or susceptible to a disease, disorder, and/or condition in accordance with a therapeutic dosing regimen, to treat the disease, disorder, and/or condition. In some embodiments, a therapeutically effective amount is one that reduces the incidence and/or severity of, and/or delays onset of, one or more symptoms of the disease, disorder, and/or condition. Those of ordinary skill in the art will appreciate that the term “therapeutically effective amount” does not in fact require successful treatment be achieved in a particular individual. Rather, a therapeutically effective amount may be that amount that provides a particular desired pharmacological response in a significant number of subjects when administered to patients in need of such treatment. In some embodiments, reference to a therapeutically effective amount may be a reference to an amount as measured in one or more specific tissues (e.g., a tissue affected by the disease, disorder or condition) or fluids (e.g., blood, saliva, serum, sweat, tears, urine, etc.). Those of ordinary skill in the art will appreciate that, in some embodiments, a therapeutically effective amount of a particular agent or therapy may be formulated and/or administered in a single dose. In some embodiments, a therapeutically effective agent may be formulated and/or administered in a plurality of doses, for example, as part of a dosing regimen.

Unless defined otherwise, technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures are for illustration purposes only, not for limitation.

FIG. 1 depicts molecular models of exemplary surfactant peptides; (A) Ac-A3K-NH₂ (SEQ ID NO:51), (B) Ac-A4K-NH₂ (SEQ ID NO:55), (C) Ac-A3KA3-NH₂ (SEQ ID NO:65). Ac-A3K-NH₂ (SEQ ID NO:51) and Ac-A4K-NH₂ (SEQ ID NO:55) have one short hydrophobic leg. Ac-A3KA3-NH₂ (SEQ ID NO:55) has two short hydrophobic legs.

FIG. 2 shows an AFM image of Ac-A6K-NH₂ (SEQ ID NO: 105) which has the typical nanotube structure of a conventional surfactant peptide.

FIG. 3 shows an AFM image of a double layer structure of Ac-A6K-NH₂ (SEQ ID NO: 105) at 0.1% (w/v). The thickness of each layer is 0.8 nm. Ac-A6K-NH₂ (SEQ ID NO: 105) formed a double layer structure at 0.1% (w/v).

FIG. 4 shows an AFM image of Ac-A3K-NH₂ (SEQ ID NO:51). Ac-A3K-NH₂ (SEQ ID NO:51) forms nanospheres at 0.1% (w/v). The diameter of the nanospheres is 28 nm.

FIG. 5 shows an AFM image of Ac-A4K-NH₂(SEQ ID NO:55). Ac-A4K-NH₂ (SEQ ID NO:55) forms nanospheres (i.e., spherical nanovesicles). The diameter of the nanospheres is 85 nm. The height profile exhibits that the edge of the nanospheres dried on the mica surface have a higher height than their middle section. This indicates that the insides of A4K (SEQ ID NO:55) nanospheres are void (i.e., forming spherical nanovesicles).

FIG. 6 shows an AFM image of Ac-A3KA3-NH₂ (SEQ ID NO:65). Ac-A3KA3-NH₂ (SEQ ID NO:65) forms nanospheres (i.e., spherical nanovesicles). The diameter of the nanospheres is 30 nm. The height profile exhibits that the edge of the nanospheres dried on the mica surface have a higher height than their middle section. This indicates that the insides of Ac-A3KA3-NH₂ (SEQ ID NO:65) nanospheres are void (i.e., forming spherical nanovesicles).

FIGS. 7A and 8B illustrate the nanostructure of surfactant peptides. In FIG. 7A, Nanotubes formed by typical surfactant peptides whose number of repeating hydrophobic amino acids is equal to 5 or more (e.g., Ac-A6K-NH₂ (SEQ ID NO:105)). In FIG. 7B, Nanospheric structure of surfactant peptides disclosed herein whose number of repeating hydrophobic amino acids is 3 or 4 (e.g., Ac-A3KA3-NH₂ (SEQ ID NO:65) and Ac-A4K-NH₂ (SEQ ID NO:55)).

FIG. 8 shows an AFM image of an A6K/siRNA complex (0.1%/0.01%). The A6K/siRNA complex aggregates.

FIG. 9 shows an AFM image of Ac-A4K-NH₂ (SEQ ID NO:55)/siRNA complex (0.1%/0.01%). The Ac-A4K-NH₂ (SEQ ID NO:55)/siRNA complex forms nanospheric structures.

FIG. 10 shows an AFM image of Ac-A3KA3-NH₂ (SEQ ID NO:65)/siRNA complex (0.5%/0.05%). The Ac-A3KA3-NH₂ (SEQ ID NO:65)/siRNA complex forms nanospheric structures.

FIGS. 11A and 11B show the cell toxicity data as described in Example 1. The luciferase emission data from the peptides only or the peptides/negative control siRNA are presented. [I] or [H] indicates the experimental condition specified in Table 4. FIGS. 11A and 11B depict the data from Method 1 and Method 2, respectively.

FIGS. 12A-12E depict the transfection efficacy data as described in Example 1. FIGS. 12A-C show luciferase emission from the control samples (e.g., mock, Dhrama-siRNA, Dhrama-NC siRNA, the peptide/NC-siRNA complex samples), the peptide/siRNA complex samples. FIGS. 12A and 12B represent the result from Method 1. FIG. 12C shows the result from Method 2. FIGS. 12D (Method 1) and 12E (Method 2) depict the suppression percentage of luciferase emission. Each luciferase emission data from the peptide/siRNA complexes has been normalized by the corresponding luciferase emission data from the peptide/NC siRNA complexes.

FIG. 13 shows zeta potentials of Ac-A4K-NH₂ (SEQ ID NO: 55)/siRIN complex at various charge ratios. The sample size was 3, and the error bars represent standard deviation (SD).

DETAILED DESCRIPTION

The present disclosure relates to surfactant peptides nanostructures and their use in delivery of agents to subjects. The present disclosure encompasses the discovery that certain surfactant peptides having hydrophobic amino acid repeats of four or fewer amino acids form nanospheric structures that are well suited for delivery of agents.

Among other things, the present disclosure identifies a shortcoming of surfactant peptides that have five or more hydrophobic amino acid repeats, in particular that they tend to form nanotube structures rather than nanospheric structures (nanosphere or spherical nanovesicle). Moreover, they tend to aggregate when complexed with agents for delivery such as siRNA. The present disclosure provides nanospheric structures that are better suited for delivery of agents to subjects, in particular siRNA or other therapeutics.

Peptides

The present disclosure provides surfactant peptide nanostructures having a small number (i.e., an integer equal to or less than four) of repeating hydrophobic amino acids. In some embodiments, peptides are provided having according to Formula I, II, III, IV, V, VI, VII, or VIII below:

(N→C): (X)a(Y)m  Formula I

(N→C): (Y)m(X)a  Formula II

(N→C): (X)a(Y)m(X)b  Formula III

(N→C): (Y)m(X)a(Y)n  Formula IV

(N→C): (X)a(Z)m  Formula V

(N→C): (Z)m(X)a  Formula VI

(N→C): (X)a(Z)m(X)b  Formula VII

(N→C): (Z)m(X)a(Z)n;  Formula VIII

-   -   wherein (X) is an amino acid having a nonpolar and noncharged         sidechain at physiological pH;     -   (Y) is an amino acid having a cationic sidechain at         physiological pH;     -   (Z) is an amino acid having an anionic sidechain at         physiological pH; and wherein     -   a is an integer equal to or less than 4;     -   b is an integer equal to or less than 4;     -   m is an integer equal to or greater than 1; and     -   n is an integer equal to or greater than 1.

In some embodiments, the amino acid of (X), (Y), and/or (Z) is a natural amino acid. In some embodiments, the amino acid of (X), (Y), and/or (Z) is a non-natural amino acid. In some embodiments, (X) is alanine, valine, leucine, isoleucine, methionine, phenylalanine, tryptophan, or glycine. In some embodiments, (Y) is arginine, lysine, histidine, or ornithine. In some embodiments, (X) is arginine and (Y) is lysine. In some embodiments, (Z) is aspartic acid or glutamic acid. The amino acids of (X), (Y) and/or (Z) may be L-amino acids, D-amino acids, or combinations thereof.

In some embodiments the number of hydrophobic repeating amino acids is four. In some embodiments, the number of hydrophobic repeating amino acids is three. In some embodiments, the number of hydrophobic repeating amino acids is two.

In some embodiments, the total number of amino acids in the peptide is from about 4 to about 10. In some embodiments, the total number of amino acids in the peptide is 4, 5, 6, 7, 8, 9, or 10.

The amino acid sequence of exemplary peptide structures is provided in Table 1.

TABLE 1 Exemplary surfactant peptides. SEQ Number ID of NO Name Sequence residues  1 A3K AAAK  4  2 KA3 KAAA  4  3 V3K VVVK  4  4 KV3 KVVV  4  5 A4K AAAAK  5  6 KA4 KAAAA  5  7 V4K VVVVK  5  8 KV4 KVVVV  5  9 A3KA AAAKA  5 10 AKA3 AKAAA  5 11 A3KA2 AAAKAA  6 12 A2KA3 AAKAAA  6 13 A4KA AAAAKA  6 14 AKA4 AKAAAA  6 15 A3KA3 AAAKAAA  7 16 V3KV3 VVVKVVV  7 17 A4KA2 AAAAKAA  7 18 A3K2A3 AAAKKAAA  8 19 V3K2V3 VVVKKVVV  8 20 A4KA3 AAAAKAAA  8 21 V4KV3 VVVVKVVV  8 22 A4KA4 AAAAKAAAA  9 23 V4KV4 VVVVKVVVV  9 24 A4K2A4 AAAAKKAAAA 10 25 V3K2V4 VVVVKKVVVV 10 26 A3D AAAD  4 27 DA3 KAAD  4 28 V3D VVVD  4 29 DV3 DVVV  4 30 A4D AAAAD  5 31 DA4 KAAAD  5 32 V4D VVVVD  5 33 DV4 DVVVV  5 34 A3DA AAADA  5 35 ADA3 ADAAA  5 36 A3DA2 AAADAA  6 37 A2DA3 AADAAA  6 38 A4DA AAAADA  6 39 ADA4 ADAAAA  6 40 A3DA3 AAADAAA  7 41 V3DV3 VVVDVVV  7 42 A4DA2 AAAADAA  7 43 A3D2A3 AAADDAAA  8 44 V3D2V3 VVVDDVVV  8 45 A4DA3 AAAADAAA  8 46 V4DV4 VVVVDVVV  8 47 A4DA4 AAAADAAAA  9 48 V4DV4 VVVVDVVVV  9 49 A4D2A4 AAAADDAAAA 10 50 V3D2V4 VVVVKKVVVV 10

In some embodiments, the peptide has an acetylated N-terminus and/or an aminated C-terminus. Exemplary peptides having an acetylated N-terminus and/or an aminated C-terminus are shown in Table 2.

TABLE 2 Exemplary surfactant peptides with aminated  C-termini and acetylated N-termini. SEQ Number ID of NO Name Sequence residues  51 Ac-A3K-NH₂ Ac-AAAK-NH₂  4  52 Ac-KA3-NH₂ Ac-KAAA-NH₂  4  53 Ac-V3K-NH₂ Ac-VVVK-NH₂  4  54 Ac-KV3-NH₂ Ac-KVVV-NH₂  4  55 Ac-A4K-NH₂ Ac-AAAAK-NH₂  5  56 Ac-KA4-NH₂ Ac-KAAAA-NH₂  5  57 Ac-V4K-NH₂ Ac-VVVVK-NH₂  5  58 Ac-KV4-NH₂ Ac-KVVVV-NH₂  5  59 Ac-A3KA-NH₂ Ac-AAAKA-NH₂  5  60 Ac-AKA3-NH2 Ac-AKAAA-NH₂  5  61 Ac-A3KA2-NH2 Ac-AAAKAA-NH₂  6  62 Ac-A2KA3-NH2 Ac-AAKAAA-NH₂  6  63 Ac-A4KA-NH2 Ac-AAAAKA-NH₂  6  64 Ac-AKA4-NH2 Ac-AKAAAA-NH₂  6  65 Ac-A3KA3-NH2 Ac-AAAKAAA-NH₂  7  66 Ac-V3KV3-NH₂ Ac-VVVKVVV-NH₂  7  67 Ac-A4KA2-NH₂ Ac-AAAAKAA-NH₂  7  68 Ac-A3K2A3-NH₂ Ac-AAAKKAAA-NH₂  8  69 Ac-V3K2V3-NH₂ Ac-VVVKKVVV-NH₂  8  70 Ac-A4KA3-NH₂ Ac-AAAAKAAA-NH₂  8  71 Ac-V4KV3-NH² Ac-VVVVKVVV-NH₂  8  72 Ac-A4KA4-NH₂ Ac-AAAAKAAAA-NH₂  9  73 Ac-V4KV4-NH₂ Ac-VVVVKVVVV-NH₂  9  74 Ac-A4K2A4-NH₂ Ac-AAAAKKAAAA-NH₂ 10  75 Ac-V3K2V4-NH₂ Ac-VVVVKKVVVV-NH₂ 10  76 Ac-A3D-NH₂ Ac-AAAD-NH₂  4  77 Ac-DA3-NH₂ Ac-KAAD-NH₂  4  78 Ac-V3D-NH₂ Ac-VVVD-NH₂  4  79 Ac-DV3-NH₂ Ac-DVVV-NH₂  4  80 Ac-A4D-NH₂ Ac-AAAAD-NH₂  5  81 Ac-DA4-NH₂ Ac-KAAAD-NH₂  5  82 Ac-V4D-NH₂ Ac-VVVVD-NH₂  5  83 Ac-DV4-NH₂ Ac-DVVVV-NH₂  5  84 Ac-A3DA-NH₂ Ac-AAADA-NH₂  5  85 Ac-ADA3-NH₂ Ac-ADAAA-NH₂  5  86 Ac-A3DA2-NH₂ Ac-AAADAA-NH₂  6  87 Ac-A2DA3-NH₂ Ac-AADAAA-NH₂  6  88 Ac-A4DA-NH₂ Ac-AAAADA-NH₂  6  89 Ac-ADA4-NH₂ Ac-ADAAAA-NH₂  6  90 Ac-A3DA3-NH₂ Ac-AAADAAA-NH₂  7  91 Ac-V3DV3-NH₂ Ac-VVVDVVV-NH₂  7  92 Ac-A4DA2-NH₂ Ac-AAAADAA-NH₂  7  93 Ac-A3D2A3-NH₂ Ac-AAADDAAA-NH₂  8  94 Ac-V3D2V3-NH₂ Ac-VVVDDVVV-NH₂  8  95 Ac-A4DA3-NH₂ Ac-AAAADAAA-NH₂  8  96 Ac-V4DV4-NH₂ Ac-VVVVDVVV-NH₂  8  97 Ac-A4DA4-NH₂ Ac-AAAADAAAA-NH₂  9  98 Ac-V4DV4-NH₂ Ac-VVVVDVVVV-NH₂  9  99 Ac-A4D2A4-NH₂ Ac-AAAADDAAAA-NH₂ 10 100 Ac-V3D2V4-NH₂ Ac-VVVVKKVVVV-NH₂ 10

Nanostructure

In some embodiments, surfactant peptides assemble to form for nanospheric structures. As used herein, nanospheric structures include structures comprising a nanosphere and/or a spherical nanovesicle. A spherical nanovesicle is similar to a nanosphere but has a center that is substantially free of self-assembling surfactant peptide.

Nanostructure plays an important role in formulation of agents (e.g., therapeutics, such as siRNA). Atomic force microscope (AFM) studies show that surfactant peptides having five or more repeating hydrophobic amino acids typically form nanotubes or double layers, as opposed to more desirable nanospheric structures. In contrast, surfactant peptides having four or fewer repeating hydrophobic amino acids were found to form nanospheric structures (e.g., spherical nanovesicles).

It has been previously reported that the nanostructure of A3K (SEQ ID NO:1) is a double layered membrane (J. Phys. Chem. B, 2014, 118 (42), pp 12215-12222). A3K (SEQ ID NO:1) has been also been reported to have nanostructures as loose peptide stacks. It has been studied for potential antibacterial capacity (Biomacromolecules, 2010, 11 (2), pp 402-411). In another report, A3K (SEQ ID NO:1), A6K (SEQ ID NO:101), and A9K (SEQ ID NO:102) were tested for interactions with lipid membranes. (RSC Adv., 2017, 7, 35973). However, unlike as reported in the references above, under appropriate conditions A3K (SEQ ID NO:1) can form nanospheric structures as shown in FIG. 4.

It has been previously reported that A4K (SEQ ID NO:5) is highly water soluble and does not exhibit relevant self-assembly in water, unlike A6K which shows self-assembly to form nanotubes. (Langmuir, 2014, 30 (33), pp 10072-10079). However, in contrast what has previously been reported, it is demonstrated herein that under appropriate conditions A4K (SEQ ID NO:5) can form nanospheric structures (spherical nanovesicles) in water as shown in FIG. 5.

A3KA3 (SEQ ID NO:15) has previously been used as a test compound for optimization of electrospray ionization condition. (Rapid Commun Mass Spectrom. 2017, 31(13):1129-1136). However, nanostructures of A3KA3 (SEQ ID NO:15) have not been described in the reference above. It is demonstrated herein that under appropriate conditions, A3KA3 (SEQ ID NO:15) can undergo self-assembly to form nanospheric structures (spherical nanovesicles) as shown in FIG. 6.

The present disclosure demonstrates the superior properties of surfactant peptides disclosed herein. Results of an experiment in which the peptides were complexed with siRNA in an aqueous solution at pH 7.5 are shown in Table 3. The peptides AAAK (SEQ ID NO: 1), AAAAK (SEQ ID NO: 5), and AAAKAAA (SEQ ID NO: 15), at peptide concentrations of 0.1% (w/v) and 0.5% (w/v), when mixed with siRNA at concentrations of 0.01% (w/v) and 0.05% (w/v), were found in a transmittance study to be transparent and substantially without phase separation. In contrast, under similar conditions, AAAAAK (SEQ ID NO: 101) and AAAAAAK (SEQ ID NO: 102) became cloudy and phase separated (see results in Table 3).

TABLE 3 Transmittance results of surfactant peptides and surfactant peptide/siRNA complexes in aqueous solution at pH 7.5. Transmittance (%) Peptide alone With siRNA 0.1% 0.5% (peptide %/siRNA %) Surfactant peptides (w/v) (w/v) 0.1%/0.01% 0.5%/0.05% A3K (SEQ ID NO: 1) 96.2 99.6 81.1 77.3 A4K (SEQ ID NO: 5) 99.4 97.8 98.7 97.5 A3KA3 99.2 97.5 98.7 88.2 (SEQ ID NO: 15) A5K^(#) 99.2 71.9 95.5 22.7* (SEQ ID NO: 103) A6K^(#) 94.8 98.7 38.4* 15.3* (SEQ ID NO: 101) A6K2A6^(#) 98.5 83.1 62.9* 12.7* (SEQ ID NO: 104) ^(#)exemplary conventional self-assembling peptides for comparison *significantly cloudy and phase-separated.

Compositions

Surfactant peptides with equal to or fewer than four repeating hydrophobic amino acids can be formulated with a variety of agents for delivery. In some embodiments, an agent is delivered to cells (in vitro delivery). In some embodiments, an agent is delivered to a subject (in vivo delivery). In some embodiments, compositions are provided comprising a surfactant peptide in an aqueous solution.

In some embodiments, the peptide is at a concentration of at least 0.01% (w/v). In some embodiments, the peptide is at a concentration of from about 0.01% (w/v) to about 0.5% (w/v). In some embodiments, the aqueous solution has a pH of from about 6 to about 8. In some embodiments, the aqueous solution has a pH of about 7.5. In some embodiments, the aqueous solution is at an ionic strength of from about 0 M to about 0.3 M. In some embodiments, the aqueous solution is at an ionic strength of about 0.15 M. In some embodiments, the aqueous solution is isotonic.

Payload Agents

In some embodiments, peptides of the invention comprise one or more payload agents, e.g., therapeutic agents or detection agents. Such agents include, e.g., a compound or entity of any chemical class including, for example, polypeptides, nucleic acids, saccharides, lipids, small molecules, metals, or combinations thereof. In some embodiments, an agent is or comprises a natural product in that it is found in and/or is obtained from nature. In some embodiments, an agent is or comprises one or more entities that are man-made in that it is designed, engineered, and/or produced through action of the hand of man and/or is not found in nature. In some embodiments, an agent may be utilized in isolated or pure form; in some embodiments, an agent may be utilized in crude form. Some particular embodiments of agents that may be utilized in accordance with the present invention include small molecules, aptamers, nucleic acids (e.g., siRNAs, shRNAs, DNA/RNA hybrids, antisense oligonucleotides, ribozymes), peptides, peptide mimetics, and the like.

Detection agents may refer to any element, molecule, functional group, compound, fragment or moiety that is detectable. In some embodiments, a detection entity is provided or utilized alone. In some embodiments, a detection entity is provided and/or utilized in association with (e.g., joined to) another agent. Examples of detection entities include, but are not limited to: various ligands, radionuclides (e.g., ³H, ¹⁴C, ¹⁸F, ¹⁹F, ³²P, ³⁵S, ¹³⁵I, ¹²⁵I, ¹²³I, ⁶⁴Cu, ¹⁸⁷Re, ¹¹¹In, ⁹⁰Y, ^(99m)Tc, ¹⁷⁷Lu, ⁸⁹Zr etc.), fluorescent dyes (for specific exemplary fluorescent dyes, see below), chemiluminescent agents (such as, for example, acridinum esters, stabilized dioxetanes, and the like), bioluminescent agents, spectrally resolvable inorganic fluorescent semiconductors nanocrystals (i.e., quantum dots), metal nanoparticles (e.g., gold, silver, copper, platinum, etc.) nanoclusters, paramagnetic metal ions, enzymes (for specific examples of enzymes, see below), colorimetric labels (such as, for example, dyes, colloidal gold, and the like), biotin, dioxigenin, haptens, and proteins for which antisera or monoclonal antibodies are available.

EXEMPLIFICATION Example 1: Use of Surfactant Peptides to Deliver siRNA to Tumor Cells In Vitro

The present Example describes, among other things, an exemplary use of surfactant peptides for delivery of siRNA to tumor cells in vitro and its cell toxicity and transfection efficacy.

siRNA (Luciferase GL3 duplex) was complexed with Ac-A4K-NH₂ (SEQ ID NO: 55), Ac-A3KA3-NH₂ (SEQ ID NO:55), Ac-A6K-NH₂ (SEQ ID NO: 105), and a control agent (DharmaFECT 1; commercially available lipid transfection agent). The siRNA and peptide complexes arranged into nanospherical structures. A composition comprising the nanospherical structures was provided to tumor cells (MCF-7 cell; breast cancer cell line) in vitro to preliminary transfection efficacy and cell toxicity.

Two methods were utilized for the present Example. For Method 1, MCF-7 cells were cultured on a plate. The siRNA and peptide complexes were added into the culture medium over the cells. The culture dish (96 wells) containing the siRNA and peptide complexes and the cells was incubated for 48 hours. For Method 2, a concentrated suspension of MCF-7 cells (5×10⁶ cells/ml) was prepared in a tube. The siRNA and peptide complexes were applied into the suspension. The cell mixture was incubated for 1 hour in the tube. The cell mixture was plated in the culture dish and incubated for 48 hours. Luciferase emission from each sample was observed.

Table 4 summarizes experimental conditions e.g., concentration of siRNA and peptide surfactants, charge ratio, and types of siRNA (e.g., Luciferase GL3 duplex or negative control thereof). The buffer used in this Example was Opti-MEM1 (serum-free). As control samples, buffer only, negative control (NC) siRNA with or without the peptide surfactants, DharmaFECT 1 with or without siRNA (or NC siRNA) were tested with the cells.

TABLE 4 Experimental conditions Experimental siRNA Surfactant Charge ratio conditions [nM] [μM] (A6K/siRNA) Remarks A 25 1.15 1.0 — B 25 3.45 3.0 — C 25 5.175 4.5 — D 25 6.9 6.0 — E 25 10.35 9.0 — F 25 15.525 13.5 — G 250 51.75 4.5 — H 25 5.175 4.5 siRNA is NC I 0 5.175 — Surfactant peptide only

Cell toxicity. For this test, the samples included NC siRNA or did not include siRNA at all. As shown in FIGS. 11A and 11B, the peptides (Ac-A6K-NH₂ (SEQ ID NO: 105), Ac-A4K-NH₂ (SEQ ID NO: 55) and Ac-A3KA3-NH₂ (SEQ ID NO:55)) exhibited a smaller decrease in luciferase emission than DharmaFECT, implying that the peptides are less toxic than DharmaFECT.

Efficacy. As shown in FIGS. 12D and 12E, luciferase emission was decreased for all surfactants at the charge ratio of 4.5, compared to siRNA only sample. The reduction of luciferase emission from the siRNA and peptide complexes was similar to the one from DharmaFECT (e.g., about 20%). An increase in luciferase emission was observed for A6K/siRNA at high concentration mixture (siRNA 250 nM, A6K 51.75 μM). The high reduction of luciferase emission from DharmaFECT may be originated from the cell toxicity.

Thus, the data in the present Example demonstrates that the peptides or the siRNA and peptide complexes are less toxic than the known transfection reagent, and the siRNA and peptide complexes delivered and effectively suppressed the target gene.

Example 2: Use of Surfactant Peptides to Deliver siRNA to Tumor Cells In Vivo

The present Example describes, among other things, an exemplary use of surfactant peptides for delivery of siRNA to tumor cells in vivo. siRNA is complexed with Ac-A4K-NH₂ (SEQ ID NO: 55), Ac-A3KA3-NH₂ (SEQ ID NO:55), Ac-A6K-NH₂ (SEQ ID NO: 105), or a control peptide. The siRNA and peptide complexes arrange into nanospherical structures. A composition comprising the nanospherical structures is administered to a mouse tumor model. One or more cancer associated genes is suppressed and the size of the tumor decreases.

Example 3: Characterization of Surfactant Peptide/siRNA Complex

The present Example describes, among other things, an exemplary characterization of surfactant peptide/siRNA complex.

Zeta potentials were measured by Zetasizer Nano ZS (Malvern) to characterize electrokinetic potential of the complex. Ac-A4K-NH₂ (SEQ ID NO:55) concentration was 0.5 w/v % in an aqueous solution. siRNA (ribophorin II, RPN2) concentration was controlled for their various charge ratios of A4K/siRNA. The zeta potential of Ac-A4K-NH₂ (SEQ ID NO:55) alone was +21.9, which represents that the surface of A4K nanosphere was positively charged because of the primary amine of lysine in Ac-A4K-NH₂ (SEQ ID NO:55). The zeta potentials of A4K/siRNA mixtures became more negative with more siRNA as shown in FIG. 13. As the equipment only detects dispersed phases larger than about 3.8 nm and the size of siRNA in water is about 2 nm in diameter, the measurement only reads the electrokinetic potential of Ac-A4K-NH₂ (SEQ ID NO:55) or Ac-A4K-NH₂ (SEQ ID NO:55)/siRNA complexes, not unassociated siRNA. As such, the result indicates that the negatively charged siRNA molecules were bounded on the positively charged surface of A4K nanospheres. Thus, the data shows that siRNA was successfully complexed with Ac-A4K-NH₂ (SEQ ID NO:55). 

1. A composition comprising a peptide having a nanospheric structure, wherein the peptide has repeating hydrophobic amino acids according to Formula I, II, III, IV, V, VI, VII, or VIII below: (N→C): (X)a(Y)m  Formula I (N→C): (Y)m(X)a  Formula II (N→C): (X)a(Y)m(X)b  Formula III (N→C): (Y)m(X)a(Y)n  Formula IV (N→C): (X)a(Z)m  Formula V (N→C): (Z)m(X)a  Formula VI (N→C): (X)a(Z)m(X)b  Formula VII (N→C): (Z)m(X)a(Z)n;  Formula VIII wherein (X) is an amino acid having a nonpolar and noncharged sidechain at physiological pH; (Y) is an amino acid having a cationic sidechain at physiological pH; (Z) is an amino acid having an anionic sidechain at physiological pH; and wherein a is an integer equal to or less than 4; b is an integer equal to or less than 4; m is an integer equal to or greater than 1; and n is an integer equal to or greater than
 1. 2. The composition of claim 1, wherein the amino acid of (X), (Y), and/or (Z) is a natural amino acid.
 3. The composition of claim 1, wherein the amino acid of (X), (Y), and/or (Z) is a non-natural amino acid.
 4. The composition of claim 1, wherein the integer of a or b is 3 or
 4. 5. (canceled)
 6. The composition of claim 1, wherein (X) is alanine, valine, leucine, isoleucine, methionine, phenylalanine, tryptophan, or glycine.
 7. The composition of claim 1, wherein (Y) is arginine, lysine, histidine, or ornithine.
 8. The composition of claim 1, wherein (Z) is aspartic acid or glutamic acid.
 9. The composition of claim 1, wherein each amino acid is an L-amino acid or a D-amino acid.
 10. (canceled)
 11. The composition of claim 1, wherein the peptide is 4-10 amino acids in length.
 12. The composition of claim 11, wherein the peptide is 5 amino acids or 7 amino acids in length.
 13. (canceled)
 14. The composition of claim 1, wherein the peptide comprises a modified N- and/or C-terminus.
 15. The composition of claim 1, wherein the peptide has an acetylated N-terminus and/or an aminated C-terminus.
 16. A composition comprising a peptide having a nanospheric structure, wherein the peptide has an amino acid sequence according to any of SEQ ID NOs: 1-50.
 17. (canceled)
 18. The composition of claim 16, wherein the peptide has an amino acid sequence of AAAK (SEQ ID NO: 1), AAAAK (SEQ ID NO: 5), or AAAKAAA (SEQ ID NO: 15). 19-20. (canceled)
 21. The composition of claim 1, wherein the peptide is in an aqueous solution.
 22. The composition of claim 21, wherein the peptide is at a concentration of at least 0.01% (w/v).
 23. The composition of claim 21, wherein the aqueous solution has a pH from about 6 to about
 8. 24. The composition of claim 21, wherein the aqueous solution is at an ionic strength of from about 0 M to about 0.3 M or to about 0.15 M.
 25. (canceled)
 26. The composition of claim 21, wherein the aqueous solution is isotonic.
 27. A composition according to claim 1 for use in drug delivery.
 28. The composition of claim 27, further comprising an agent for delivery to a subject.
 29. The composition of claim 28, wherein the agent is a therapeutic, a drug, or an siRNA. 30-31. (canceled)
 32. The composition of claim 29, wherein the siRNA is for delivery to a cancer cell.
 33. A method of formulating an agent for delivery to a subject, the method comprising a step of contacting the agent with a composition according to claim
 28. 34. A method of delivering an agent to a subject, the method comprising administering to the subject a composition formulated with a peptide, wherein the peptide has repeating hydrophobic amino acids according to Formula I, II, III, IV, V, VI, VII, or VIII below: (N→C): (X)a(Y)m  Formula I (N→C): (Y)m(X)a  Formula II (N→C): (X)a(Y)m(X)b  Formula III (N→C): (Y)m(X)a(Y)n  Formula IV (N→C): (X)a(Z)m  Formula V (N→C): (Z)m(X)a  Formula VI (N→C): (X)a(Z)m(X)b  Formula VII (N→C): (Z)m(X)a(Z)n;  Formula VIII wherein (X) is an amino acid having a nonpolar and noncharged sidechain at physiological pH; (Y) is an amino acid having a cationic sidechain at physiological pH; (Z) is an amino acid having an anionic sidechain at physiological pH; and wherein a is an integer equal to or less than 4; b is an integer equal to or less than 4; m is an integer equal to or greater than 1; and n is an integer equal to or greater than
 1. 35-63. (canceled) 